The two pensioners are said to have died of heart attacks at the same time on the Great Barrier Reef (File image)

A third French diver was later initially suspected to have also had a heart attack.

But the man was later thought to have had an anxiety attack and recovered, McKenzie said.

He explained: “He watched two of his travel companions in massive trouble. It would give anybody heart palpitations.”

McKenzie claimed Passions of Paradise has taken more than 400,000 tourists to the reef since 1989, with the company's only previous fatality being an 80-year-old who died from a heart condition in 1997.

Police are preparing a report for a state coroner, who will determine the official causes of the deaths.